Adventures in Science: How to Use a Multimeter

Just getting into electronics or want a refresher on digital multimeter basics? We've got you covered.

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My New Years resolution was to make more videos. A lot more videos.

OK, it really had nothing to do with the new year, but it sounded good in my head.

Based on the feedback I received for my concept series last year, I’ve decided to spend some time on a more basic concept and tutorial video series (and implement many of the suggestions you all gave). I want to leave the more advanced electrical design concepts for According to Pete, so I plan to focus on the basics: how to use tools, broad concepts, and maybe some programming.

First up: How to Use a Multimeter. This incredibly useful tool should be one of the first devices you pick up if you’re getting started in electronics. Basic models are capable of measuring AC and DC voltages, current and resistance. You’ll also find yourself using it quite often to detect unwanted shorts and opens in your circuits.

SparkFun sells a few different multimeters to get you started. If you want the absolute best, be prepared to spend some money, and you can’t really do much better than a Fluke. I use a Fluke 87V as my personal meter at home, but I had to scour eBay deals to wait for one to show up used at a reasonable price.

If the written word is your preferred method of digesting information, Nate has a great tutorial on using multimeters:

How to Use a Multimeter

January 9, 2015

Learn the basics of using a multimeter to measure continuity, voltage, resistance and current.

I’m hoping to continue these tutorial and concept videos (almost) every week. What things would you like to see? What are some concepts that you consider to be essential in starting with electronics, programming, crafting, etc. that aren’t covered elsewhere?


Comments 16 comments

  • I was taught that when measuring resistance you should not be on parallel with the device. This because the human body has its own resistance and it will get into the measure.

    • Correct, you really shouldn’t be touching the metal parts of the probes if you don’t want to introduce your body’s resistance, unlike what I did in the video :) However, because your body’s resistance is so high, it has a negligible effect on measuring smaller resistances (e.g. 2.2kΩ).

  • It looks like there’s a written tutorial for soldering, but a short video might be nice. It’s always good to see the right way to use tools beyond just some text.

    Attaching wire ends (barrel jacks, PWM, quick-release ends) would be interesting, but it’s probably not something that most people would use on a regular basis.

    • Thanks for the suggestions! We’ve got a good number of soldering videos, but if there’s a specific technique (or one you want to see re-done), I can definitely add it to the list. Dealing with wires would be good, especially things like how to properly crimp (I still have trouble with that sometimes).

  • I would have been thrilled by “How NOT to use a multimeter”.

  • I have an idea for a future episode. It isn’t electronics, but it is a tool that is commonly used by makers:

    Calipers

    Start with a quick introduction to the types (vernier, dial, digital) and if there is time a quick primer in reading a vernier scale. Then go through the different ways (don’t just describe, but demonstrate) to use it, especially touching on some of the more advanced techniques.

    • That’s a good one–I’ll add it to the list! Even for electronics, I use mine all the time, especially on SMD parts that don’t have good documentation on the footprint.

  • Shawn,

    Great video! Keep up the good work!

    FWIW, about 5 minutes before I went to Sparkfun.com this morning, I realized that last night I’d used a DMM to check the voltage of a battery, and forgot to turn it off. (This is the most frequent problem I have with DMMs! Yeah, I know, the more expensive ones have an “auto-off” feature, though “feature” is pronounced “flaw”.)

    These days, DMMs can be VERY inexpensive. If you watch the ads (such as in snail-mail), you can often get one for a whopping $0.00 (i.e., “free”) with purchase of anything else at Harbor Freight. True, they’re not really great meters, but I’d say they’re good enough for more than 95% of what I need – e.g., checking batteries (the aforementioned 9V one only read 7.75, which explains why the smoke detector was complaining), verifying that I read the color bands correctly on a resistor, checking continuity, and such. I do have a Fluke for when I either need more accuracy, or need to work on higher voltages. (I’m not comfortable using that $0.00 DMM on a 600V DC solar array circuit that can hit 8 Amps.)

    One other limitation of the not-extreme-high-end DMMs is the inability to accurately measure low resistance values (say below about 5 ohms). You need to use “4-wire” for these (two wires supply the “forcing current”, and two do the voltage measurement). I used such meters back in the mid-70s as an electronics tech in a factory. Within the past couple of months, I had the opportunity to acquire a 5-½ digit DMM from an “estate sale”, but since the last calibration sticker on it is from 95, I’m not sure it’s been powered up in the past 20 years. I haven’t had time yet to get out the Variac and bring it up slowly (reforming the power supply capacitors).

    Oh, yes: another reason for checking resistors is that they sometimes “drift with age” – to the point where one author referred to “carbon composition” resistors as “carbon decomposition” resistors. Which also reminds me: if you’re using a DMM that can do capacitance, and try to measure an electrolytic, polarity IS important (unless the cap is one of the non-polarized versions).

    One more thing: I’ve suggested this to our friends at Adafruit, but maybe SparkFun could get them as a product: wires (maybe about 12" long) with banana plugs on one end, and the “male” pin on the other end to plug into a solderless breadboard. Yeah, you can use a short wire and alligator clips, but I’ve had a lot of trouble with that over the years with shorts and/or the clips falling off or losing contact.

    • More thoughts: A good reason to have the “cheapies” around is that sometimes it is useful to be able to make two (or more) measurements “simultaneously”, for instance, watching both the “input” and the “output” of a circuit, or measuring both the current and the voltage at the same time.

      Also, with the “cheapies”, it’s no big loss if they happen to get destroyed – which is why I keep one of the “Harbor Freight specials” in the car – useful for doing things like checking the battery voltage, or checking continuity on a fuse or lightbulb, etc., but if it “goes for a swim” (or has some other disaster), I haven’t lost a lot.

      • Yes! That is exactly the reason I keep that old Radio Shack DMM around. It also fits nicely into the roll-up tool bags we sell.

  • I would like to see a video on the basics of open source. I have been in circles when the question has come up and it would be nice to have a link to forward sometimes. Also, EMI, PIDs, and maybe some “historic reasoning” would be nice.

    • This is a great idea. We talk about open source a lot, but nailing down exactly what it means can get a little muddled. Shawn and I will add it to the queue!

  • Include options for measure methods. Example Amps: clsmp meters (AC & DC) and in series. Additional series methods would be series internal / external (for large currents) to the meter. Also electronic modules that do amplification or conversion to digital data via SPI, I2C and magic smoke communication protocols.

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